I can't speak for the author, but I made the transition from JS+React to TypeScript+React to Elm and it "changed my mind" too. When I started with React/Redux,

I can't speak for the author, but I made the transition from JS+React to TypeScript+React to Elm and it "changed my mind" too. When I started with React/Redux, I didn't know much about functional programming, but I developed a certain interest... A couple years later my React stack was full of tools and libraries that allowed me to write my React apps in a more functional manner. I used TypeScript for the type system, ImmutbaleJS for immutable data structures, Ramda as a FP utility library and Recompose to call React itself in a functional manner. I also used pure stateless components exclusively... Then I switched to Elm and I realized, that the React stack I was working with was a crippled version of Elm. I'm currently writing my first app in Elm and it feels much smoother.